The present invention relates to apparatuses and methods for non-invasive bioparameter monitoring and, more particularly to a combination non-invasive and invasive bioparameter measuring device and method.
A 2006 summary of the failed non-invasive glucose monitoring techniques entitled “The Pursuit of Noninvasive Glucose: Hunting the Deceitful Turkey” (“The Pursuit of Noninvasive Glucose” or “PNG”) written by John Smith, former chief scientific officer at Lifescan, a Johnson & Johnson subsidiary, details why over the last 25 years there has not been a successful non-invasive glucose monitoring device. This background discussion is based primarily on this book.
Diabetes is a serious disease that can cause eye damage, kidney damage, loss of feeling in the extremities, slow healing of wounds, amputation of toes, feet or legs and cardiovascular disease. See PNG at page 7. If patients adhere strictly to a proper diet, exercise, take medication and make frequent measurements of blood glucose they are able to maintain their health and lead relatively normal lives. Id. It is therefore critical to monitor blood glucose. To accurately measure blood glucose levels, one needs to measure the amount of glucose in the blood itself (as opposed to the urine) and this is done by dedicated devices for measuring blood glucose level invasively at home or in doctors' offices and laboratories millions of times every day. See Id. Such devices require painful intrusion, which is uncomfortable and carries a risk of contamination for the individual. Sticking oneself with a sharp object to draw blood is unpleasant and even traumatic, especially since it must be done repeatedly daily over many years.
In addition, in order for people with diabetes to maintain healthy levels of glucose there has always been a need for simple, accurate tests that patients can perform at home. See id. If simple, non-invasive, inexpensive, reliable tests were available, they could measure their glucose non-invasively often at home. See id.
According to “The Pursuit of Noninvasive Glucose”, each year, hundreds of thousands of people are newly diagnosed with diabetes, because rising standards of living in the developed world encourage a diet prone to high glucose. The immense market size (as of 2007 over $7 billion worldwide) and the demand has led to constant announcements by fledgling companies that the problem of a non-invasive blood glucose monitoring system has been solved. In fact, no successful device has yet been developed to allow patients to measure their glucose non-invasively without pain or trauma. According to “The Pursuit of Noninvasive Glucose” oxygen saturation is measured by the ratio of the amount of hemoglobin that has oxygen attached to the amount that does not have oxygen attached. Oxy hemoglobin is bluish while deoxyhemoglobin is a visibly different color, namely bright red. Significantly, hemoglobin is the only compound in the body with a strong blue or red color and it exists almost exclusively inside red blood cells, which travel inside blood vessels in well-defined paths. It is therefore relatively easy to use spectroscopic techniques to measure oxygen saturation in the body non-invasively.
In contrast to hemoglobin, glucose has nondescript characteristics—it is colorless, it varies in concentration from one part of the body to another and it exists in much smaller concentrations than hemoglobin. See PNG at pages 26-28. Furthermore, the chemical structure of glucose as a hydrocarbon with multiple hydroxyl groups also makes it very similar to many other compounds in the body and in fact glucose is attached to most of the proteins in the body. Spectroscopic techniques for detecting glucose have had difficulty distinguishing signals of protein molecules that are attached to glucose and which may correlate with glucose from signals of glucose molecules alone. For example, the near infrared region has many weak, overlapping, varying spectroscopic signals that come from hydrocarbons with multiple hydroxyl groups.
Moreover, the spectroscopic signals reflected from light striking glucose molecules are weak. Accordingly, when attempting to find correlations between a data set and a true glucose measurement, it is very hard to successfully use mathematical algorithms to separate variations within the data set into a series of curve shape components to account for decreasing amounts of observed variability.
In addition, spectroscopic techniques often show initially promising correlations between variations of a spectroscopic effect with true glucose concentrations but when later checked against variations in room temperature and humidity, it turns out that these local environmental variations account for the correlation. See The Pursuit of Noninvasive Glucose at p. 66. As a result, no reliable and accurate technique ends up getting developed.
A further problem is that to determine how well a parameter is a good measure of glucose concentration, the procedure is to have the patient drink 50 to 100 grams of glucose in a single drink will not be effective because “almost every measured physiological parameter (i.e. core temperature, surface temperature, peripheral perfusion, skin hydration, electrolyte balance, gastric motility, peripheral edema, enzyme levels, galvanic skin response, respiration, urine production, saliva production) shows strong correlation with the curve in an oral glucose tolerance test”. See The Pursuit of Noninvasive Glucose at page 60.
“Noninvasive glucose measurements have been attempted by an incredibly diverse range of technologies.” The Pursuit of Noninvasive Glucose at p. 28. None of them have succeeded during the last 25 to 30 years. Although correlations between certain qualities and glucose have been alleged to have been found using spectroscopic analysis, no non-invasive product using such techniques have to date ever been successful or even workable in terms of accurately and reliably measuring glucose. See The Pursuit of Noninvasive Glucose. This may be because the alleged correlations were never real to begin with since they were not verified in light of environmental or other parameters. No method of calibrating data from a non-invasive measurement to predict the actual glucose level in the body based on invasive measurements as the reference point has succeeded to a reliable and accurate point.
Besides glucose, there are many other bioparameters that it would be useful to be able to monitor accurately and reliably, particularly by a portable device usable by a consumer or a patient at home. Such bioparameters can for example include oxygen and carbon dioxide concentration, urea nitrogen, systolic and diastolic blood pressure, moisture, dryness, saltiness, pH, tissue saturation (for example external skin tissue, internal muscle), tissue vitality (for example internal tumor tissue or external skin melanoma represents different skin vitality) red blood cell count (number or concentration of cells per one cubic millimeter), stroke volume variation (amount of blood injecting out from the heart in every stroke) and skin vessel deformation, cholesterol, potassium, systolic and diastolic blood pressure, stroke volume, chloride, sodium, nitrogen, hemoglobin, bilirubin, cholesterol LDL, HDL and total cholesterol, percentage of CO2, percentage of O2, red blood cells, white blood cells, iron, hematocrit, platelets, etc.
There is therefore a compelling need for an accurate and reliable apparatus and method for a non-invasive bioparameter measuring device, particularly where glucose is the bioparameter, although not limited to such a case. There is a further need for such an apparatus and method which is portable enough and easy enough to use that it may be usable by patients at home.